What is Spinal Anesthesia?

Anesthetic drugs are injected into the subarachnoid or epidural space of the spinal canal, and the spinal nerve root is blocked to cause the corresponding area innervated by the nerve root to have an anesthetic effect, which is collectively called intraspinal anesthesia. According to the injection location, it can be divided into subarachnoid anesthesia (also called spinal or spinal anesthesia), epidural anesthesia, combined spinal and epidural anesthesia, and sacral block anesthesia.

Basic Information

English name

intraspinal anesthesia

Visiting department

Department of Anesthesiology

Subarachnoid anesthesia

The method of injecting local anesthetic into the subarachnoid space to block the spinal nerves to cause anesthesia in the corresponding area dominated by it is called subarachnoid block, referred to as spinal anesthesia.

2. Epidural block

The method of injecting local anesthetic into the epidural space to produce segmental spinal nerve block and causing anesthesia in the corresponding area dominated is called epidural block, referred to as epidural block or epidural anesthesia. Divided into single and continuous epidural anesthesia.

3. Anesthesia with sacral block

A type of epidural blocker. Local anesthetic is injected into the iliac lumen through the sacral hiatus to block the sacral spinal nerve. Commonly used for anal and perineal surgery. Due to the rich distribution of nerves in the sacral canal, the incidence of local anesthetic toxicity was slightly higher than that of epidural blocks. Suitable for rectal, anal and perineal surgery, but also suitable for pediatric abdominal surgery.

4. Combined spinal and epidural anesthesia

Anesthesia combined with spinal epidural anesthesia, referred to as combined spinal-epidural anesthesia, is currently widely used in clinical lower abdominal and lower limb surgery. Combined anesthesia shows the advantages of rapid onset of spinal anesthesia and perfect analgesic motor nerve block. At the same time, it also exerts epidural anesthesia with intermittent catheter delivery to meet the needs of long-term surgery. CSEA is a combination of low-dose spinal anesthesia and suitable epidural anesthesia. As long as the block plane is controlled below 10 chests, the hemodynamics is stable, and it is safe for elderly patients with other systemic diseases and high-risk maternal patients. It is particularly advantageous to perform hip or lower limb surgery on older patients with more severe comorbidities, which has obvious advantages over other anesthesia methods.

Generally, one-point puncture is used, and L2-3 or L3-4 is punctured with a special combined puncture needle. Two-point puncture can also be taken, namely, T12-L1 puncture the epidural tube, L2-3 or L3-4 subarachnoid puncture anesthesia.

Physiological mechanism of spinal canal anesthesia

Drug action site

During subarachnoid anesthesia, local anesthetics selectively act on the anterior and posterior roots of the exposed spinal nerves, partly on the surface of the spinal cord, and the epidural block mechanism is more complex. Local anesthetics pass through the paravertebral tissue and subarachnoid block The pathway acts on the spinal nerve and spinal cord surface ^[1] .

2. Nerve block sequence

Different nerve fiber block orders are different, usually sympathetic nerve cold sensation temperature sensation temperature recognition sensation dull pain sensation sharp pain sensation motor sensation (muscle loose) proprioception disappears. Therefore, after anesthesia, the patient usually feels fever, numbness, numbness, pain, and movement to the proprioceptive sensation of the lower extremities or hips (ie, the existence of the lower extremities is not felt).

3. Impact on the body

(1) During the spinal canal anesthesia of the cardiovascular system , the sympathetic nerves are blocked, which reduces the peripheral vascular resistance caused by the expansion of the small arteries in the innervated area; the venous expansion increases the volume of the venous system, so the return of blood volume occurs. Decreased, lower cardiac output leads to lower blood pressure. However, the occurrence of hypotension and the decrease in blood pressure are closely related to the size of the blockade, the patient's general condition, and the body's ability to compensate. High block levels, a wide range of anesthesia, and inadequate compensatory capacity of the patient's circulatory system are the main reasons for blood pressure drop after block ^[2] .

(2) The effect of spinal anesthesia on respiratory function on the respiratory system mainly depends on the extent and degree of blockage of the spinal nerves that control the intercostal and diaphragm muscle motor functions. When most or all of the intercostal muscles are paralyzed, pulmonary ventilation can be affected to varying degrees. Once the phrenic nerve is also blocked, it can cause severe hypoventilation or stop breathing.

(3) The sympathetic nerve is blocked during the spinal anesthesia of the digestive system , the vagus nerve is relatively hyperactive, and the gastrointestinal motility is enhanced, which can cause nausea and vomiting. When the abdominal viscera is pulled by surgery or the blood pressure drops rapidly and the decline is large, the central ischemia and hypoxia can excite vomiting, and the middle pull can also cause nausea and vomiting.

(4) After sympathetic nerve block of the lumbosacral part of the urinary system , the urethral sphincter contracts, while the detrusor muscle relaxes, which can cause urinary retention.

Spinal anesthesia

Generally, the patient is selected in the lateral lying or sitting position (saddle block), the back is perpendicular to the bed surface, and is flush with the bed edge. The waist is bent as far as possible to make the spinous process gap open to facilitate puncture. Taking spinal anesthesia as an example, L3-4 or L2-3 gaps are generally used. First, localize, then infiltrate the interspinous ligament of the skin and subcutaneous tissue anesthesia layer by layer to reduce puncture pain. According to the condition and the habit of the anesthesiologist, direct or side puncture is selected. The successful puncture is the cerebrospinal fluid outflow and anesthetic is injected into the subarachnoid space. For the control of anesthesia plane, the skin is often tested with pain or cold saline swabs to test the block plane. Block plane control is an important part of subarachnoid block anesthesia. In a very short time, the plane is controlled to the range required for surgery. There are many factors that affect the plane, such as the height of the puncture gap, the height and weight of the patient, the body position, the type, concentration, dose, volume, and specific gravity of the local anesthetic drug, the direction of the oblique mouth of the needle, and the injection speed. Therefore, after a successful puncture, the anesthesiologist often asks the patient to cooperate, determine the sensory plane, adjust the position and adjust the block plane to achieve the perfect anesthesia effect.

Indications for spinal anesthesia

Subarachnoid anesthesia

It is mostly suitable for surgical anesthesia of the lower abdomen, lower limbs and perineum within 2 to 3 hours, such as lower limb surgery, hemorrhoidectomy, and cesarean section.

2. Epidural block

Various abdominal, waist, pelvic and lower limb surgeries, as well as superficial surgery on the neck, upper limbs and chest wall can also be applied. Epidural anesthesia can be used for spinal anesthesia. Clinically, epidural block is also used in the adjuvant treatment of coronary heart disease, vascular occlusive disease, herpes zoster, and painless delivery.

Contraindications to spinal anesthesia

Subarachnoid anesthesia

Diseases of the central nervous system such as spinal cord multiple sclerosis, meningitis, spinal deformity and trauma, spinal tuberculosis and tumors, shock, sepsis, skin infections near the puncture site, and coagulation disorders are all considered contraindications to spinal anesthesia. Should be used with caution.

2. Epidural block

As with subarachnoid anesthesia, central nervous system diseases such as meningitis, spinal deformity and trauma, spinal tuberculosis and tumors, shock, sepsis, skin infections near the puncture site, and coagulation dysfunction are considered contraindications. Clinically there is breathing Difficult patients should not choose cervical and thoracic epidural anesthesia. Menstrual women, patients who are taking anticoagulant drugs such as aspirin, should not use this anesthesia because it affects coagulation function.

Spinal canal anesthesia with certificate

Subarachnoid anesthesia

(1) Abnormal conditions during anesthesia Failure of anesthesia is too slow or the body position is adjusted improperly, the needle is taken out without proper dose, the drug solution is mixed into the blood to reduce the drug effect, and the high pH of the cerebrospinal fluid causes the drug solution to precipitate, etc. Anesthesia is not effective or even fails, and may require re-anaesthesia or a change in anesthesia such as general anesthesia. The blood pressure decreased and the anesthesia level increased significantly. The occurrence of hypotension and the decrease in blood pressure are closely related to the size of the blockade, the patient's general condition and the body's ability to compensate. The effects of spinal anesthesia with respiratory depression on respiratory function mainly depend on the range and extent of spinal nerve block that governs intercostal and diaphragm muscle function. When most or all of the intercostal muscles are paralyzed, pulmonary ventilation can be affected to varying degrees. Once the phrenic nerve is also blocked, it can cause severe hypoventilation or stop breathing. Nausea and vomiting are mainly caused by hypoxia caused by circulation inhibition of hypotension, excitement of nausea and vomiting center, sympathetic block after anesthesia, stimulation of gastrointestinal motility caused by vagal nerve excitement, and stimuli such as surgical traction also easily cause vomiting.

(2) Complications after anesthesia Headaches are more common complications. Headaches disappear more than 6 to 24 hours after the anesthesia disappears. They are most severe in 2 to 3 days, and usually disappear in 7 to 14 days. A few patients can last 1 to May is even longer. For those with mild headache, they can disappear on their own for 2 to 3 days. Moderate daily rehydration is 2500 to 4000ml. Small doses of analgesic and sedative drugs are used. In severe cases, epidural hyperemia filling therapy can be used. Urinary retention is mostly caused by the late recovery of the innervating bladder nerve, which may also be related to lower abdominal surgery stimulation, perineal and anal surgery pain, and the patient is not used to bedtime urination. Severe catheterization. The rare serious complications of paralysis of the lower limbs are mostly caused by adhesive arachnoiditis, and the treatment effect is poor. The cauda equina syndrome cannot be recovered for a long time, sensory movement of the lower limbs, fecal incontinence, sphincter paralysis of the urethra, etc. are involved.

2. epidural anesthesia

(1) Penetrating the dura mater

(2) Total spinal anesthesia puncture needle or epidural catheter was mistakenly inserted into the subarachnoid space. Excessive drug injection caused extensive blockage. Clinical manifestations showed no pain in all spinal nerve innervation areas, hypotension, loss of consciousness and respiratory arrest, and even heartbeat Sudden arrest and death of patients are serious complications.

(3) Nerve root injury When nerve roots are injured, patients often complain of electric shock-like pain and conduct to unilateral limbs. It is characterized by pain and numbness in the innervated area of the injured nerve, and the typical symptoms are accompanied by cough and numbness of the pain when belching is exacerbated. It usually relieves or disappears within 2 weeks, but the numbness remains for several months.

(4) Epidural hematoma is caused by epidural hemorrhage with extremely low probability of formation (0.0013% to 0.006%), but it is the main cause of paraplegia caused by epidural anesthesia.

(5) Difficulty or breakage of other catheters, blood pressure drop, respiratory depression, etc.

References

1. Wang Junke, Surgery (Chapter 13 Anesthesia), People's Medical Publishing House

2. Luo Ailun, Spinal Canal Anesthesia, China Encyclopedia Press